When using a toothbrush to brush one's teeth, it is important to clean the contact line between the teeth and the gums. Effective brushing is obtained when the brush is moved (back and forth) horizontally (at a certain angle). Horizontal brushing along the said contact line is easy and simple when it is performed on the outer side of the teeth (the side facing the cheek). It is, however, more difficult and cumbersome to brush the inner side of the teeth (the side facing the tongue), and especially along the inner curvature of the front teeth. In addition, effective brushing of the back (posterior) molars is also a known problem. The toothbrush, subject of the invention, offers a good and effective solution to the above problems.